This invention relates to a solenoid valve device and more particularly to an improved solenoid operated fuel injection valve.
In the interest of improving fuel economy and exhaust emission control for internal combustion engines, the use of fuel injection is widely accepted. One particularly popular form of fuel injector employs a pintle or poppet type valve which is operated by an electrical solenoid. In order to control the opening of the valve, the solenoid cooperates with an armature which is normally rigidly affixed to the valve stem and when energized is attracted to the solenoid to open the poppet valve. When the solenoid is deenergized, a spring urges the valve to its closed position. Due to the high speed of fuel injection, the movements aforenoted (opening and closing) occur quite rapidly. One difficulty in connection with the use of solenoid operated valves is that the mass of the armature, which is normally affixed to the upper end of the valve stem and remotely from its valving surface, causing elongation of the valve stem upon closing. When the elongated stem returns to its normal length, a force is created on the valve which tends to effect its opening. Hence, a characteristic known as "bouncing" has become accepted with this type of valve.
However, the subsequent openings of the valve after the main injection cycle can give rise to numerous problems. Of course, this will affect the control of the amount of fuel that is delivered to the engine. More importantly, however, the bouncing operation can cause fuel to be injected at the time when ignition is occurring. When this happens, ignition may occur more rapidly and less uniformly than is desired and a condition known as "misfire" can occur.
An arrangement has been proposed so as to try to minimize the affect of bouncing of a solenoid operated valve by having the armature slideably supported on the valve stem. The armature contacts a stop on the valve stem for moving the valve in an opening direction but contacts a fixed abutment when moving in the closing direction and the armature moves independently of the valve stem. Although this tends to reduce bouncing, in some instances it can not only not provide adequate bouncing protection but may even aggravate the problem. For example, when the sliding armature contacts the fixed stop it will be forced back against the valve stem and can urge the valve stem toward its opened position.
It is, therefore, a principal object of this invention to provide an improved injector valve assembly for a fuel injection system wherein bouncing of the valve element is substantially eliminated.
It is a further object of this invention to provide an improved solenoid operated injection valve wherein the connection between the armature and the valve stem permits relative movement to eliminate or substantially bouncing.